DRAM circuits include an array of memory cells arranged in rows and columns. Each of the rows and columns is driven by a respective row decoder and column decoder. Often, the memory circuits include several redundant rows and columns that are used as substitutes for defective locations in the memory array.
In the manufacture of DRAM and other integrated circuitry, redundant circuit elements are often provided in the event not all the circuitry or components prove operable upon testing. Thus, if some portion of the circuitry is inoperable, backup circuitry is available for proper operation of the integrated circuit. One manner of providing for such circuit redundancy may be achieved by using antifuses and redundant circuit logic for activating (“blowing”) such antifuses. An antifuse is essentially the opposite of a fuse. Fuses are conductive in an un-blown state, and become non-conductive barriers to current flow upon being “blown”. Antifuses, on the other hand, block current flow in the un-blown state, and become conductive upon being “blown”. Antifuses are composed of a pair of conductors separated by any suitable dielectric. To “blow” the antifuse, a certain level or quanta of charge (QBD) is passed through the antifuse dielectric to cause a physical breakdown of the intervening antifuse dielectric material. Such creates permanent electrically conductive paths between the conductive elements, thus forming a desired electrically conductive short. In antifuse operation, upon initial application of voltage suitable to cause an initial short through the antifuse dielectric, the initial conductive path which is formed may not be sufficient. Accordingly, a suitable “soak” current is applied across the blown dielectric to cause further intermixing or diffusion of the two conductors through the dielectric to assure making a suitable conductive path through the antifuse dielectric.
Accordingly, QBD and soak current values where it is desired to blow an antifuse are impacted by the antifuse dielectric material, its dimensions, and physical design of the antifuse. Dielectrics are also used in other electronic devices, such as a capacitor dielectric in a capacitor and as a gate dielectric in the gate of a field effect transistor. Dielectric properties for one or both of capacitors and transistor gates for optimization of capacitors or transistor gates might result in undesired (QBD) and soak current values of desired antifuse constructions.